1. Field of the Invention
The present invention relates to a program response time estimating apparatus that estimates the length of time (response time) to elapse after a program enters an execution wait state until the execution is completed. In particular, it relates to a program response time estimating apparatus that may be employed in an information processing system with a plurality of executable programs present therein, in which each program enters an execution wait state at a given time point and the programs in an execution wait state are sequentially executed in the order of their cutoff times.
2. Description of the Related Art
In an information processing system or an information communication system, for instance, a plurality of executable programs may be present within the system. In such a case, the programs enter an execution wait state at various time points. Programs in an execution wait state are sequentially executed in the order they entered the execution wait state or in the order of their cutoff times
Let us consider a system which sequentially executes programs in an execution wait state in the order of their cutoff times. Such a system is disclosed in, for instance, xe2x80x9cScheduling Algorithms for Multiprogramming in a Hard Real-time Environment,xe2x80x9d Journal of the Association for Computing Machinery, Vol. 30, No. 1, January 1973, pp.46-61, by C. L. Liu et al. In this type of system, a program is executed in advance to measure its response time for purposes of estimating the program response time. Alternatively, a program may be executed in a simulation by employing an apparatus such as that disclosed in Japanese Unexamined Patent Publication No. 1994- 95931 to obtain the program completion time point.
In addition, if it is known in advance that the intervals over which program execution requests are received or the program execution time conforms to a specific probability distribution function, and execution sequence control is implemented whereby programs are not executed in the order of their cutoff times but in the order in which they enter an execution wait state, for instance, the program response time can be estimated in correspondence to a parameter of the probability distribution function that expresses the interval upon which the program enters an execution wait state and the execution time.
Information processing systems include those with cutoff times set for program execution and those without any specific cutoff times. When a new program is to be added to a system of the former type, for instance, there is a need to verify in advance the length of time that the program requires to complete its processing.
In such a case, in a system adopting execution sequence control through which the programs are executed in the order of their cutoff times, a need exists to estimate an approximate if not perfectly accurate program response time. In order to meet this need, it is necessary to actually execute the program or simulate the program execution sequence based upon the numerical value representing the length of execution time to obtain the program response time. It takes a great deal of time to determine the response time through actual execution of the program or through simulation.
Accordingly, an object of the present invention is to provide a structure capable of estimating a response time of a program within a short period of time without having to actually execute the program or implement a simulation.
In order to achieve the object described above, the response time estimating apparatus according to the present invention constitutes a program response time estimating apparatus that is employed in a system with a plurality of programs present therein and estimates the response time of any of the programs. In the system, each program enters an execution wait state at a given time point. The system sequentially executes the programs in an execution wait state in the order of their cutoff times.
The response time estimating apparatus according to the present invention is provided with an average execution request arrival interval holding unit that holds an average interval after which a request to execute a program present within the system is received. The average interval after which a program execution request is received may be either provided by the system user each time or may be calculated by monitoring the individual programs with the average execution request arrival interval holding unit. In addition, when a new program is added to a system that is already in operation, the user or the average execution request arrival interval holding unit re-calculates an average interval after which an execution request is received with respect to all the programs in the system after the introduction of the new program based upon information on the added program and on the programs that are already operating in the system.
In addition, the response time estimating apparatus according to the present invention is provided with an average execution time holding unit that holds an average of the lengths of execution time of the programs present in the system. The response time estimating apparatus according to the present invention is further provided with an average relative cutoff time holding unit that holds a length of time to elapse after a request for execution of a program present in the system arrives until its cutoff time. The average execution time and the length of time to elapse after an execution request is received until the corresponding cutoff time may be also provided by the user or may be calculated by monitoring the individual programs with the average execution time holding unit. When a new program is added, the user or the average execution time holding unit re-calculates these values with respect to all the programs in the system after the introduction of the new program.
Furthermore, the response time estimating apparatus according to the present invention is provided with an estimation-undergoing program execution time holding unit and an estimation-undergoing program cutoff time holding unit, which respectively hold the length of execution time of a program whose execution completion time is to be estimated and the length of time to elapse between the execution request arrival time point and the cutoff time with respect to the program whose execution completion time is to be estimated.
By employing the individual means described above, the response time estimating apparatus according to the present invention estimates an execution completion time point for a program whose execution completion time is to be estimated.